Various types of thermally actuated relays have heretofore been proposed, such as described in U.S. Pat. No. 3,842,382 and U.S. Pat. No. 4,184,136. Such relays utilize direct heating of a bimetal element to actuate a switch. The thermal element utilizes a strap which expands and contracts as it is heated and cooled by a heater to bend a spring member which is designed to provide an over center snap-action.